1. Field of the Invention
The present invention relates to a control apparatus for an automatic clutch device which assures stable operations of the automatic clutch device even when there is a change of the output of the engine of an automobile and a change in characteristics of the engine due to the aging of the structural elements.
2. Discussion of Background
FIG. 4 is a block diagram showing a conventional belt-driven type speed changing machine. In FIG. 4, a reference numeral 2 designates a speed changing machine and a numeral 2A designates a belt.
The belt 2A is extended between a driving side fixed pulley member 6 and a driven side fixed pulley member 12. A driving side pulley assembly 4 is mainly composed of the driving side fixed pulley member 6 and a driving side movable pulley member 8.
A driven side pulley assembly 10 is mainly composed of the driven side fixed pulley member 12 and a driven side movable pulley member 14.
The driving side fixed pulley member 6 of the driving side pulley assembly 4 is fixed to a rotary shaft 16. The driving side movable pulley member 8 is mounted on the rotary shaft 16 so as to be capable of moving in the axial direction of the shaft 16, but to be incapable of rotating.
The driving side movable pulley member 8 and the driven side movable pulley member 14 are respectively provided with first and second housings 18, 20 so that first and second oil chambers 22, 24 are respectively formed by the first and second housings.
A pushing means 26 such as a spring is provided in the second oil chamber 24 so as to push the second housing 20 in the direction of expanding the second oil chamber 24.
An oil pump 28 is provided on the rotary shaft 16. The oil pump 28 is communicated with the first and second oil chambers 22, 24 through first and second oil conduits 30, 32 respectively.
A primary pressure control valve 34 is provided in the first oil conduit 30. The primary pressure control valve 34 is a speed changing control valve for controlling a primary pressure known as an input shaft sheave pressure.
A constant pressure control valve 38 for controlling the line pressure (generally 5-25 kg cm.sup.2) to be a constant pressure (3-4 kg/cm.sup.2) is connected through a third oil conduit 36 to the first oil conduit 30 which is at the side of the oil pump 28 with respect to the primary pressure control valve 34. The primary pressure control valve 34 is also communicated with a first threeway electromagnetic valve 42 for controlling primary pressure through a fourth oil conduit 40.
An intermediate of the second oil conduit 32 is connected to an intermediate of a seventh oil conduit 54 through a fifth oil conduit 46, and the fifth oil conduit 46 is connected to a sixth oil conduit 48 through a line pressure control valve 44 which has a pressure releasing function so as to adjust the line pressure. The line pressure control valve 44 is communicated with a second three-way electromagnetic valve 50 for controlling the line pressure through the sixth oil conduit 48.
The seventh oil conduit 54 is communicated with an eighth oil conduit 56 through a clutch pressure control valve 52 for controlling a clutch pressure. The eighth oil conduit 56 is communicated with a third three-way electromagnetic valve 58 for controlling a clutch pressure.
The first three-way electromagnetic valve 42 for controlling clutch pressure, the second three-way electromagnetic valve 50 for controlling clutch pressure and the third three-way electromagnetic valve 58 for controlling clutch pressure are respectively connected to a ninth oil conduit 60, and they are respectively communicated with the primary pressure control valve 34, the line pressure control valve 44 and the clutch pressure control valve 52. An end of the seventh oil conduit 54 is communicated with the second oil chamber 24.
The clutch pressure control valve 52 is communicated with an oil clutch 62 through a tenth oil conduit 64 and is communicated with a pressure sensor 68 through a eleventh oil conduit 66. The pressure sensor 68 detects an oil pressure in the oil clutch 62 wherein the detected oil pressure can be used for a target clutch pressure when the clutch pressure is controlled in a hold mode or a start mode.
In a drive mode, the clutch pressure becomes equal to the line pressure. Accordingly, the detection of the clutch pressure contributes for the control of the line pressure.
An input shaft revolution detecting gear wheel 70 is provided at the outside of the first housing 18, and a first revolution detecting device 72 placed at the side of an input shaft is provided near the outer circumference of the input shaft revolution detecting gear wheel 70. On the other hand, an output shaft revolution detecting gear wheel 74 is provided at the outside of the second housing 20, and a second revolution detecting device 76 placed at the side of an output shaft is provided near the outer circumference of the output shaft revolution detecting gear wheel 74.
Detection signals from the first and second revolution detecting devices 72, 76 are transmitted to a control section (ECU) 82, whereby a revolution speed of engine and a belt ratio are obtainable.
The oil clutch 62 is provided with an output transmitting gear wheel 78, and a third revolution detecting device 80 is provided near the outer circumference of the output transmitting gear wheel 78 to detect the revolution of the output shaft of the final stage. The third revolution detecting device 80 detects the revolutions of a reduction gear device and a differential gear, a driving mechanism and the final output shaft directly connected to a tire, by which a car speed can be detected. Further, it is possible to detect the revolutions before and after the oil clutch 62 by the cooperation of the second and third revolution devices 76, 80, which contributes the detection of a quantity of slip in the clutch.
The control section 82 receives a signal of a throttle opening degree in a carburetor (not shown) and various signals concerning revolution speed of the engine, car speed or the like to thereby change the duty ratio, hence, speed change control can be effected. The control section 82 controls the opening and closing operations of the first three-way electromagnetic valve 42, the constant pressure control valve 38, the second and third three-way electromagnetic valves 50, 58 and the pressure sensor 68.
Signals inputted to the control section 82 and the function of the input signals are as follows.
(1) Signals to detect the position of a shift lever
Signals indicating each range of "P", "R", "N", "D" or "L" which are used for controlling the line pressure required for each of the ranges, duty ratios and the oil clutch.
(2) Signals indicating degrees of opening of a throttle valve in a carburetor
The signals are used for detecting engine torques from memories previously inputted in a program and determining a target engine revolution or a target duty ratio.
(3) Signals for detecting idling positions in the carburetor
The signals are used for correcting a carburetor throttle opening degree sensor and for increasing accuracy in the control.
(4) Signals concerning an accelerator pedal
The signals are used for detecting the intention of a driver on the basis of a state of depression of an accelerator pedal and for determining optimal control at the time of cruising or starting.
(5) Signals of a brake
The signals are used for detecting the presence or absence of the depressing of a brake pedal and for determining optimal control for the separation of the clutch.
(6) Signals concerning options such as power mode
The signals are used for options such as changing the performance of an automobile into, for instance, sports car feeling (or economical use).
The control section 82 is to receive a detection signal on car speed NCO, and to switch a speed-change control system from an open-loop control to a closed loop control even in a normal start mode when the car speed NCO exceeds a predetermined value such as a car speed trigger value NCOTR.
A numeral 84 designates a piston disposed in the oil clutch 62, a numeral 86 designates a ring-like spring, a numeral 88 designates a first pressure plate, a numeral 90 designates a friction plate, a numeral 92 designates a second pressure plate, a numeral 94 designates an oil pan, a numeral 96 designates an oil filter, and a numeral 69 designates an oil temperature sensor for detecting the temperature of pressure oil so that the output of the oil temperature sensor is outputted to the control section 82.
The operation of the conventional control apparatus will be described.
In the belt-driven type continuous speed changing machine 2, the oil pump 28 mounted on the rotary shaft 16 is operated in response to the actuation of the rotary shaft 16, and oil in the oil pump 28 is supplied from the oil pan 94 located at the bottom of the speed changing machine through the oil filter 96.
A pressure by the oil pump 28, i.e. a line pressure is controlled by the line pressure control valve 44. Namely, when an amount of leakage in the line pressure control valve 44, i.e. a quantity of oil released from the line pressure control valve 44 is large, the line pressure becomes low. On the contrary, when the quantity is small, the line pressure becomes high.
The line pressure control valve 44 has speed control characteristics wherein the line pressure is changed in three stages: a full low state, a full overtop state and a ratio fixing state. The operation of the line pressure control valve 44 is controlled inclusively by the second three-way electromagnetic valve, and the line pressure control valve 44 is actuated in response to the operation of the second three-way electromagnetic valve 50.
The second three-way electromagnetic valve 50 is controlled with a duty ratio at a constant frequency. Namely, a state of duty ratio being 0% is a state that the second three-way electromagnetic valve 50 is not operated at all wherein the output side is communicated with the atmosphere and the output oil pressure is zero. A state of duty ratio being 100% means a state that the second three-way electromagnetic valve 50 is actuated so that the output side is isolated from the atmosphere and the pressure of the electromagnetic valve 50 becomes the same as a controlling pressure, i.e. the maximum output oil pressure. The oil pressure is changed by the duty ratio. Accordingly, the characteristic of the second three-way electromagnetic valve 50 is substantially linear and it is possible to operate the line pressure control valve 44 in an analogous fashion, whereby the duty ratio of the second three-way electromagnetic valve 50 is changed desirably to thereby control the line pressure.
The second three-way electromagnetic valve 50 is controlled by the control section 82. The primary pressure used for speed changing is controlled by the primary pressure control valve 34, which is controlled inclusively by the first three-way electromagnetic valve 42 in the same manner as the line pressure control valve 44.
The first three-way electromagnetic valve 42 is used for communicating the primary pressure with the line pressure, or for communicating the primary pressure with the atmospheric pressure. Further, it functions to shift the belt ratio to the full over drive state by communicating the primary pressure with the line pressure, or to shift to the full low state by communicating the primary pressure with the atmospheric pressure.
On the other hand, the clutch pressure control valve 52 controls the clutch pressure, and when the maximum clutch pressure is needed, it communicates the system with the line pressure side, and when the lowest clutch pressure is needed, it communicates the system with the atmospheric pressure side.
The clutch pressure control valve 52 is controlled inclusively by the third three-way electromagnetic valve 58 in the same manner as the line pressure control valve 44 and the primary pressure control valve 34, and therefore description will be omitted.
The clutch pressure is changed in a range from the lowest atmospheric pressure (zero) to the maximum line pressure. For the control of the clutch pressure, there are four basic patterns. The basic patterns are as follows.
(1) Neutral mode
The position of a shift lever corresponds to "N" or "P" wherein the clutch is in a completely separate state, and the clutch pressure shows the lowest pressure (zero).
(2) Hold mode
The position of the shift lever corresponds to "D", "L" or "R" which is in a low pressure level in a case that, for instance, a driver doesn't intend to drive without operating a throttle lever, or he decelerates the speed during cruising by separating the engine torque. In this case, the clutch is not entirely in contact with the engine torque, but rather is barely in contact therewith.
(3) Start mode
This corresponds to a state that the automobile is about to start or the clutch is again connected after the brakings of the clutch. In this state, the clutch pressure is at a suitable level so as not to cause the engine to malfunction and to produce an appropriate engine torque (clutch input torque) so that the automobile can be operated smoothly.
(4) Drive mode
The automobile is in a normal cruising state and the clutch is completely coupled. The clutch pressure is kept at a high level so as to be sufficiently durable to a high engine torque.
The neutral mode (1) among the basic patterns is effected by a switching valve (not shown) operable in association with shifting operations, and other basic patterns (2), (3) and (4) are-effected by the duty ratio control of the first through third three-way electromagnetic valves 42, 50, 58 by the control section 82. Especially, in the drive mode (4), the seventh oil conduit 54 is communicated with the tenth oil conduit 64 by means of the clutch control valve 52 to thereby produce the maximum pressure, whereby the clutch pressure becomes the same as the line pressure.
The primary pressure control valve 34, the line pressure control valve 44 and the clutch pressure control valve 52 are respectively controlled by output oil pressures from the first through third three-way electromagnetic valves 42, 50, 58. An oil pressure to control the first through third electromagnetic valves 42, 50, 58 is a constant oil pressure which is produced at a constant pressure control valve 38. The control oil pressure is lower than the line pressure, however, it provides a stable constant pressure. Further, the control oil pressure assures stable operations of the primary pressure control valve 34, the line pressure control valve 44 and the clutch pressure control valve 52.
In the following, description will be made as to electronically controlling the conventional belt-driven type continuous speed changing machine 2. The operation of the belt-driven type continuous speed changing machine 2 is controlled by oil pressure, wherein a belt holding function, a line pressure for-suitably transmitting a torque, a primary pressure used for changing a speed change ratio and a clutch pressure for certainly coupling the clutch are respectively given on the basis of instructions from the control section 82.
FIG. 5 is a block diagram showing the internal construction of the control section 82 which has a feed back system and a feed forward system. In FIG. 5, the control duty for speed change is 0% in the start mode. In controlling the line pressure, a target line pressure is determined in a target line pressure determining means 111 depending on a throttle opening degree .theta., and the output of the target line pressure determining means 111 is supplied to a first order lag filter 112 at which the target line pressure valve is subjected to a first order lag. The output of the first order lag filter 112 is supplied to a pressure/duty converting means 113 at which a duty corresponding to the target pressure value determined and a line pressure control duty is outputted. The above-mentioned is a brief description concerning the feed back control system on engine speed.
In the next, description will be made as to a clutch pressure control duty in the feed forward control system. In controlling the clutch pressure, a target engine speed is determined in a target engine speed determining means 103 depending on a throttle opening degree .theta.; the signal of the target engine speed determining means 103 is passed through a first order lag filter 104 at which a first order lag filtering treatment is conducted, and the output of the first order lag filter 104 is supplied to a subtractor 105. In the subtractor 105, a subtracting operation of the output of the first order lag filter 104 and an actual engine speed Ne is conducted to obtain an error, which is supplied to a PI control means 106. The PI control means 106 receives the output of the subtractor 105, i.e. the error between the target engine speed and the actual engine speed Ne and carries out proportion and integration calculations. As a result of the calculations, an output from the PI control means 106 is supplied as a target pressure correcting value to a subtractor 107.
On the other hand, in a feed forward loop, a temporary target clutch pressure is determined in a feed forward quantity determining means 101 depending on a throttle opening degree .theta., and the temporary target clutch pressure value is subjected to a first order lag filtering treatment in a first order lag filter 102, whereby the output of the filter 102 is supplied to the subtractor 107. The subtractor 107 conducts subtracting calculations of the temporary target clutch pressure from the target pressure correcting value so that the temporary target clutch pressure is corrected by the target pressure correcting value, and the corrected value is outputted as a new target clutch pressure to a subtractor 108. The subtractor 108 subtracts the target clutch pressure value from an actual clutch pressure Pc to obtain an error, and the error is outputted to a PID control means 109.
The PID control means 109 conducts calculations of proportion, differentiation and integration, and a result of the calculations is outputted to a subtractor 110. The subtractor 110 subtracts the output of the PID control means 109 from an offset duty value to obtain an error as a clutch pressure control duty which is treated as a manipulated variable.
FIG. 6 is a diagram showing a relation of throttle opening degree to target engine speed in the target engine speed determining means 103.
The feed forward quantity determining means 101 operates and outputs a clutch pressure capable of transmitting an engine torque, which corresponds to a target engine speed which is determined by a throttle opening degree .theta..
FIG. 8 is a diagram prepared by adding target engine speed curves to an engine characteristic diagram, by which a target engine speed corresponding to a throttle opening degree and a nominal engine torque Ten corresponding to the target engine speed are obtainable.
In the feed forward quantity determining means 101, a feed forward quantity can be obtained from the following steps: throttle opening degree-target engine speed-nominal engine torque-necessary clutch transmission torque-conversion of clutch pressure as shown in FIG. 8, FIG. 7 (a characteristic diagram showing a relation of clutch oil pressure to clutch transmission torque and FIG. 9 (characteristic diagram showing a relation of throttle opening degree to feed forward quantity).
In the above-mentioned conventional belt-driven type speed changing machine, the following disadvantage is found. The characteristics of an engine change due to conditions of use, environment, and a change of the structural elements with time, non-uniformity of the elements. Further, the output of an engine changes depending on conditions of operation of accessories and an electric load. Further, there are a change and scattering of clutch oil pressure/transmission torque characteristics as shown in FIG. 7. When an error in a feed forward quantity (a temporary target clutch pressure) becomes large due to the causes as described above, a correcting value obtained by the feed back loop is insufficient (there is a limit in the correcting value since there is an upper limit in a control gain of the feed back loop rather than the stability of the feed back loop), and there causes a time lag. Accordingly, the revolution of an engine tends to blow up due to a delay in clutch coupling, or a shock of clutch coupling is resulted because the clutch coupling is too fast, whereby a driver feels uneasy feeding of the engine. In the worst case, the engine is stopped.